BCG Vaccination and Interpretation of Purified Protein Derivative Test Results

Abstract

The purified protein derivative (PPD), or tuberculin, test is a reliable means to determine whether a person has active tuberculosis or has been exposed to the disease. In a previously sensitized individual, the intracutaneous injection of the protein-lipopolysaccharide component of Mycobacterium tuberculosis causes a type IV delayed hypersensitivity reaction. We were consulted about an immigrant patient with results of a PPD test that were strongly positive but who had no remarkable chest radiograph findings. We found controversy about whether to recommend chemoprophylaxis. Specifically, there was confusion regarding whether to account for a possible previous BCG vaccination as responsible for the positive PPD test results. Therefore, we reviewed the literature and present our findings. Report of a Case. A 32-year-old Pakistani man (who immigrated to the United States more than a decade ago) was admitted to the hospital because of a severe reaction at the site of a PPD test. He